linux: fix pahole discovery when BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE

Around Linux 5.11, upstream started introducing checks that execute
"pahole --version" for feature discovery (e.g. [1]).

However, when building with BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE Buildroot
only lists host-pahole in LINUX_DEPENDENCIES, so it isn't available for
the configure step when using BR2_PER_PACKAGE_DIRECTORIES. This results
in the host pahole being used (resulting in host-dependent behavior), or
no pahole being detected at all when the build host doesn't have it
(which will then disable Kconfig options that require it).

Fix this by adding host-pahole to LINUX_KCONFIG_DEPENDENCIES.

A similar issue occurs when running "make linux-menuconfig" and friends
because PATH deliberately gets stripped when pkg-kconfig.mk builds
x_CONFIGURATOR_MAKE_ENV. Explicitly pass the pahole path to fix this.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=5f9ae91f7c0dbbc4195e2a6c8eedcaeb5b9e4cbb

Signed-off-by: Florian Larysch <fl@n621.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 6c9c2b71e6)
Signed-off-by: Raphaël Mélotte <raphael.melotte@mind.be>

linux/linux.mk

@@ -125,6 +125,7 @@ endif
 
 ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE),y)
 LINUX_DEPENDENCIES += host-pahole
+LINUX_KCONFIG_DEPENDENCIES += host-pahole
 else
 define LINUX_FIXUP_CONFIG_PAHOLE_CHECK
 	$(Q)if grep -q "^CONFIG_DEBUG_INFO_BTF=y" $(KCONFIG_DOT_CONFIG); then \
@@ -387,6 +388,9 @@ LINUX_KCONFIG_EDITORS = menuconfig xconfig gconfig nconfig
 # therefore host-ccache would be ready, we use HOSTCC_NOCCACHE for
 # consistency with other kconfig packages.
 LINUX_KCONFIG_OPTS = $(LINUX_MAKE_FLAGS) HOSTCC="$(HOSTCC_NOCCACHE)"
+ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE),y)
+LINUX_KCONFIG_OPTS += PAHOLE="$(HOST_DIR)/bin/pahole"
+endif
 
 # If no package has yet set it, set it from the Kconfig option
 LINUX_NEEDS_MODULES ?= $(BR2_LINUX_NEEDS_MODULES)